Measuring and controlling system



Sept. 19, 1961 F. M. ALEXANDER MEASURING AND CONTROLLING SYSTEM Filed Nov. 8, 1957 i I' I A mm mm om v I INVENQTOR United States Patent 3,000,438 MEASURING AND CONTROLLING SYSTEM Frank M. Alexander, Columbus, Ohio, assignor to Industrial Nucleonics Corporation, a corporation of Ohio Filed Nov. 8, 1957, Ser. No. 695,416 4 Claims. (Cl. 162259) This invention relates to continuous web or sheet forming apparatus such as paper making machinery, and more specifically it relates to improved means for controlling the widthwise formation of webs produced by a machine having a plurality of local profile adjustments.

The invention will be illustrated and described in connection with a paper making machine of the Fourdrinier type, although it will be understood that such illustration and description are merely exemplary, in that the principles and the means provided by the invention may be as well adapted with little or no modification to other industrial processes wherein similar control problems are existent.

For background information contributing to an understanding of the present invention in relation to the illustrative embodiment thereof given herein, reference is made to U.S. Patent No. 2,779,253, issued January 29, 1,957, to Thomas M. Owens. Accordingly only a very brief description of the details of the paper making machine per se is deemed necessary in the present specifica tion.

j In Fourdrinier machines, the paper stock is discharged:

from the head box onto a forming Wire through an adjustable opening which controls the rate of flow and amount of the stock being deposited on the forming wire. This openingis defined by the head box apron, side walls and an adjustable slice or slice assembly which can be moved towards or away from the apron to regulate the size of the opening. It is known that the flow of stock may vary in density across the discharge opening. The desired uniformity of the sheet profile suffers thereby, and may also be affected adversely by variations in the moisture removal operations across the'width of the Fourdrinier wire section. Accordingly the slice is frequently provided with some kind of a flexible slice plate or lip having a plurality of local contour adjustments over the length thereof to compensate for variations that would otherwise occur in the distribution of pulp across the width of the forming wire. If a proper setting of all these adjustments can be maintained under all operating conditions, it is theoreticmly possible to produce a paper sheet having a uniformly flat and level profile thickness.

At the present time, any obvious irregularities in the profile thickness can be corrected only by a rather unsatisfactory manual slice adjustment procedure which is described in some detail in the above referenced patent to Owens. The quality of results obtained by such a procedure is dependent solely on the skill of the paper ma-. chine operator, and said adjustment is considered at this time to be a part of the art of paper-making.

In accordance with this invention in one preferred form thereof, each of the plurality of slice contour adjustments is individually equipped for motorized Vernier adjustment, for example, by replacing the hand wheels 70 of the Owens Patent 2,779,253 with a worm and gear arrangement adapted to be driven by an electric motor. Operation of these motors is automatically controlled by the signal from an accurate thickness gauge measuring the paper web.

'It is recognized that the basic concept per se of automatic stock flow control in accordance with paper thickness measurements is well known, as is evidenced for example by U.S. Patents 1,757,867, 1,768,088 and 2,576,614 of Lewellen et al'. While apparatus exemplified by these patents has not proved entirely successful, primamas Patented Sept. 19, 1961 marily due to the lack of an accurate measuring device, the basically practicable concepts set forth have been well developed by others in recent years. For example, very satisfactory stock flow control has been achieved by the use of an improved type of radiation thickness gauge described in U.S. Patent No. 2,790,945, to H. R. Chope, in combination with an improved controller such as is described in a 'co-pending application Serial No. 688,720, filed October 10, 1957, by D. E. Varner, now U.S. Patent No. 2,895,888 particularly in connection with FIG. 2, of the said application.

The present invention does not necessarily contemplate replacement of the presently available controls of the type described, since automatic control of total stock flow from the head box is still required in order to maintain the proper basis weight of the paper. On the other hand, this invention has for its purpose the maintenance of uniformity in the profile of the sheet widthwise, whereas the presently available controls permit the maintenance of uniformity only lengthwise thereof.

More specifically in accordance with this invention it has been found that each of the separate slice contour regulating adjustments primarily aifects the paper web" profile thickness at a rather definite portion of the Width of the web, so that the paper sheet may be considered to consist of a laterally contiguous series of relatively narrow strips, each of which can be more or less inde pendently controlled as to thickness by an adjustment of the corresponding portion of the slice directly upstream thereof.

At the earliest point in the paper making process where the paper web can be made self-supporting for a short distance, there is provided a thickness gauge, preferably of the type comprising a radioactive source and radiation detector positioned on opposite sides of the Web, said gauge being mounted on a traversing track and automat ically programmed to scan from side to side across the entire width of the sheet in a repeating sequence.

As each of the strips or areas of the traveling web, is scanned by the gauge, a variable electrical signal rep-v resenting the error in the thickness of the strip is integrated by an electronic device to provide a further signal indicative of the average thickness error in the strip. When the gauge has completed the scan of the particular area, the integrated signal is switched to the input of an automatic controller which operates the motor controlling the spacing of the corresponding slice portion with respect to the head box apron.

-In order that the measuring and controlling operations may proceed efliciently and without undue delay, the invention preferably employs three integrators and as many separate motors as there are slice regulating adjustments,- for example, twelve, although only one traversing gaugev and master controller are required. Thus if the slice adjustments are numbered in sequence from one to twelve and the gauge is measuring across area number three, the. third integrator will be integrating the error in thickness of area number three, the second integrator will be feed ing the previously determined area number two average thickness error reading into the controller so as to correct the setting of slice regulator number two, and integrator number one will be in process of resetting to zero in preparation to receive the error signal to be obtained as a result of the impending measurements of area num-. ber four.

It is the principal object of this invention to provide antomatic means for controlling the cross-sectional dimension profile of laterally extended products such as sheet' materials which are continuously formed by a manufacturing machine.

It is also an object to provide means for automatically eliminating variations which otherwise occur between different points spaced across the width of such product.

It is another object to provide automatic means for regulating a plurality of laterally spaced, local contour adjustments each determining a cross-sectional dimension at only a portion of the width of such product.

It is still another object to provide means in accordance with the above objects wherein the plurality of local contour adjustments can be effected sequentially in accordance with measurements provided by a single gauging means adapted to traverse the entire width of the laterally extended product.

It is a further object to provide means in accordance with the above objects wherein control of each individual profile adjustment is effected in accordance with measur ments of only that portion of the product most directly affected by said adjustment.

It is a still further object to provide means in accordance with all the above objects wherein control signals are derived from integrated average measurements rather than instantaneous measurement.

It is yet another object to provide apparatus in accordance with the above objects which is relatively economical to build, readily adapted for installation on existing process machines, simple to operate and requiring a minimum of adjustment and maintenance.

Other objects and advantages will become apparent from the following general and then detailed description read in conjunction with the accompanying drawings wherein the single figure is a partly schematic and a partly diagrammatic .view of the present invention and its relation to the paper making process.

Referring to the single figure, there is shown a general scheme of the wet section of the Fourdrinier paper making process. A sheet of paper stock 100 is shown in the process of formation by machinery including a head box 102 wherefrom a laterally extended flow of paper stock is discharged through an adjustable slice lip 104. Stock input to the head box is indicated generally at 106. The paper stock passes onto a wire 108 passing over the breast roll 11% after which moisture is removed from the distributed paper stock through both capillary and gravitational action by means not shown. The mat leaves the wire 108 at the couch roll 11( and passes through the presses 118 and 120. Immediately following thepresses, the sheet 100 is shown to pass through a non-contacting thickness gauge at 130. Further description of the paper making process is not included, as it will not be an influencing factor on the control invention herein described.

A thickness gauge 130 comprises a U-bracket 131 supporting a source of radiation in a lower housing located directly under an upper head 132 and below the sheet 100. The lower housing is attached to the lower arm of the U-bracket 131 so that it remains directly under the upper housing 132. Thus when the gauge is driven to its maximum on-sheet position as hereinafter described, the source and detector housings occupy the positions shown by the dotted lines, whereby the housing containing the radiation source is indicated at 133b, and the upper housing is indicated at 132a. A radiation detector such as an ion chamber is located in the upper housing 132 to accept penetrative radiation passing upward through the sheet thereby generating a thickness-functional voltage which is transmitted over line 135 to measuring circuits located at 136. The gauge 130 traverses the Width of the sheet 100 on a rail 129 by means of a transversing motor 134 actuated by a scanning control circuit shown at 138. Sheet 100 is hypothetically illustrated as being divided width-wise by dotted lines into six equal areas represented by letters a through 1, beginning at the starting position shown, over area a at the right-hand edge of the sheet 100 and continuing across to the left-hand edge of the sheet 100. Directions are denoted as seen by an observer facing the slice-lip opening of the head box 102.

It can be seen that each of the imaginary areas or strips a through 1 in the general gauging area is located directly downstream from a corresponding, individually adjustable portion of the slice section 104. In general, therefore, the paper thickness in each area can be controlled more or less independently by varying the spacing between the head box apron (not shown) and the corresponding localized portion of the slice.

When the gauging head 132 is positioned at the righthand edge of the sheet 100, the scanning control 138 will actuate the traversing motor 134 to slowly move the gauge to the left. The gauge will sequentially scan areas a, b, c, d, e, and f, in its continuous movement over the sheet. Upon completion of the scanning of area f, the motor 134 is reversed by the scanning control 138 so that the gauge is rapidly re-positioned over the righthand edge of the sheet 100. As soon as this position is attained, the gauge will brake and initiate another scanning sequence over areas a through 7.

A voltage signal representing paper stock thickness at the traversing point of measurement is produced by the gauge 130 and transmitted over line 135 to the gauge circuitry shown generally at 136. Circuit 136 is fully described in the above referenced U.S. Patent No. 2,790,- 945, issued April 30, 1957, to H. R. Chope.

Shown generally by the numeral 30 is a comparison bridge network mechanically linked to the strip chart recorder mechanism associated with the measuring circuitry at 136, said mechanism and linkage being actuated by a chart motor 21. Bridge network 30 effects a comparison between the instantaneous measured stock thickness and a desired or target thickness. A voltage signal representing any stock thickness error is produced and presented by bridge circuit 30 to the averaging device shown generally at 40. A multitap rotary position switch at 10 directs the averager 40 by means of relay contacts to sequentially integrate the signal representing the average error of each profile section a through f as the sheet is scanned. The averager 40 in turn presents this integrated signal representing the arithmetic mean of a section profile error over line 53 to a control system shown generally at so which actuates, in an amount proportional to the error, the slice position motor as shown at 70 in such a direction as to correct the error in profile.

The system as hereinabove generally described provides an automatic adjustment to the slice for any desired number of scans across the width of the sheet 100. Re-adjustment of a slice is performed after each separate area scan by the gauge 130.

Referring to the heretofore mentioned measuring circuitry shown generally at 136, a profile voltage signal therefrom is presented to the XY recorder chart drum motor 21. Motor 21 reversibly rotates the chart drum 22 through a mechanical linkage line 23 in an amount corresponding to any change in the weight per unit area of sheet passing between the radioactive source and detector. The chart pen 24 is moved laterally along the chart 26 by a mechanical coupling 12 to correspond with the traversing position of the gauge 130 across the sheet 100. Widthwise sheet profiles are thereby recorded on the chart 26 for each scan of the sheet 100.

Referring back to the gauge 130, there is shown with the traversing motor 134 and mechanical linkage line 12, a rotary position switch 10 receiving power from a suitable supply as at 11 through a power switching circuit shown generally at 8. The switch arm 13 is adjusted to sequentially actuate relays 1 through 6 as the gauge 130 scans areas a through f of the paper sheet 100. That is, relay 1 will be energized while the gauge is scanning area a on the sheet 100, and so on. The relay contacts hereinafter described will utilize the same position numbering system. Separate contacts of the same relay will be denoted with the number of the relay followed by different lower-case letters. Contacts of relay 6 will be 6a, 6b, 6c, 6d, etc.

To de-energize relays 1 through 6 while the gauge 13.0

is returning to the right-hand edge of sheet 100, power to relays 1 through 6 is removed when the gauge 130 has completed the scanning of area f. This is accomplished by the switching circuit 8 which removes power from the rotary switch arm 13 and applies it to relay 7. Switching circuit 8 is actuated by the scanning control circuit at 138 by means of line 139. Power is disconnected from relay 7 and re-applied to the switch arm 13 when the gauge 130 begins scanning area a.

A signal representing the thickness error is developed in the bridge circuitry shown generally at 30. Herein a slidewire arm 31 is shown to be positioned in its slidewire mounting 32 through a mechanical connection 25 to the XY recorder motor 21. Power is supplied to the bridge by a battery 33, and overall bridge voltage is controlled by a potentiometer at 34. A voltage representing the desired stock thickness, or target thickness is set on the inner arm slidewire 35 from mechanical connection 36 by adjusting an indicator knob as at 37. The adjustment at 37 can be made to read in pounds per ream or any desirable profile units. The bridge is grounded through potentiometer 35 at 38. An error voltage or signal representing any difference between the existing and target thickness-of stock is now produced by the bridge '30 along line 39 to be presented to the averaging deviceshown at 40. This slidewire, therefore, is capable of developing an independent voltage signal representative of the existing stock thickriess error at any point of traverse of the gauge 130.-

The averaging circuitry 40 is here shown divided into three identical averaging networks or integrators although any plurality of the same could be provided to fulfill the objectives of the invention. Contacts 1a through 6a allow fer a successive programming of the integration function, in that said function is herein performed in turn on each of the traversing areas a through 7 on the paper stock sheet 100. Briefly described, the averaging function involves a series of three simple operations: integration, reading out and re-setting. The three functions are then the basis for the circuitry to be described herein.

The mean integrator in its preferred form comprises a stabilized operational amplifier as at 47 utilizing an inverse feedback principle and having an-input potentiometer as at 50 and a capacitor 44 coupling the output 47b of amplifier 47 to its input 47a. By closure of a set of relay contacts 30, a shunt resistance 41 may be connected across capacitor 44 in order to discharge the same, thereby resetting the integrator. The integrating operation is carried out in the above fashion by each of the three separate identical inte-: grators incorporated in the averager 40. The sequential operation of each is described hereinbelow.

As the gauge 130 traverses area a, an error voltage signal is continuously transmitted over line 39 to the averaging device 40 from the bridge network 30. Contacts 111' and 1b are closed, as relay 1 is energized by the switch 10, respectively thereby connecting line 39 to the input circuit of amplifier 47 and discharging capacitor 46. A charge is built up on capacitor 44 by the error signal until the gauge 130 moves to area b, and the switch de-energizes relay 1, opening contacts 1a and 1b and energizes relay 2. At this timecontacts 2a and 2b will close, and the voltage on capacitor 44"applied through contact 2b and line 53 to the control system shown generally at 60. As the above read-out function occurs, contact 2a permits an error voltage charge to accumulate on capacitor 45 with any error signal voltages from area b of sheet 100 until the gauge 130 reaches area 0. As the rotary switch 10 energizes relay 3, contacts 2a and 2b are opened, while contacts 3a, 3b and 3c areclosed.

Error voltage from area :2 charges capacitor 46 through contact 3a, thus bringing the third integrator into use. An error signal charge from area 0 is built up on capacitor 46 while the voltage on capacitor 45 of the second integrator having been fed from amplifier 48, is directed through contact 3b and line 53 to the control system at 60. As contact 3c closes, capacitor 44 of the first inte- ,eesess grator is 'dischargedthrough' resistance 41 thereby resetting the integrator and preparing it to receive error signals from area d through contact 4a.

As the gauge continues its traverse across the stock sheet 100, contacts 4a through 6a are arranged to charge in sequence capacitors 44, 45 and 46 again, following which, contacts 5b through 7b serve to read-out the integrated signal over line 53. Contacts 60, 7a and 1b are programmed to re-set the integrators in the same sequence as contacts 3c, 4c and 50 were arranged.

Through the hereinabove described relay program each of the three integrating networks is operated twice for each complete scan of the gauge 130 over sheet 100. Relay 7 is not energized while the gauge 130 is slowly scanning right to left, but only on the return sweep of the gauge, when it serves to read-out capacitor 46 and to discharge capacitor 45 by means of contacts 7b and 7a, respectively. Sensitivity is adjusted and amplifiers 47, 48 and 49 are matched, with potentiometers 50, 51 and 52.

The utilization'of the above described averager provides a voltage signal at line 53 which can be interpreted as the arithmetic mean of all profile errors for a prede termined portion of the sheet 100.

The controller 60 is designed in, accordance with principles well known to those skilled in the industrial control art, and consists of an error sensing circuit 61, an on time circuit 62 and a relay control circuit 63. A line 53 connects the error sensing circuit 61 to the averaging. device 40 and a line 64 couples the output of the relay control circuit 63 to the relay control circuit 63 to the relay contacts 2d, 3d, 4d, 5d, 6d and 7d, each of which is attached to a separate slice motor. The on time circuit 62, connected between the error sensing circuit 61- and the relay control circuit 63, determines the maximum length of time in which any slice motor is permitted to operate in accordance with the magnitude of error sig nal on line 53.

. The error sensing circuit contains a suitable electromechanical switch responsive-to variations in phase of the error signal and provides the necessary power to operate the heavy duty relays in the relay control circuit, 63. The output of the relay control circuit 63 will operate any slice motor electrically connected to line 64 by means of the aforementioned relay contacts in a direction and for a length of time determined by the polarity and magnitude of the error signal. It must also be noted that the slice motors 71 through 76 are coupled to gearing devices 71g .through 76g for the purpose of reducingfor purposes of correction is not performed until the area over which the correction is to be made has been completely scanned and the error signal has been integratedi Proceeding with an exemplary instance of profile measurement assume that the sheet thickness of area a, area b and area 0 is heavier than the desired or target thickness and that the gauge 130 begins to scan area a. The measuring signal transmitted to the gauge circuitry 136 is reproduced on the graph 26 as a line under the first po-j sition (left side of chart) which lies above the target line; Chart roll 22 is rotated by chart motor'21 as the pen is drawn hor'montally across it by the traversing motor 134 thereby producing this trace. also causes the slidewire arm 31 to be positioned to one side of the center balance position of the slidewire bridge 30 so that an error voltage of a certain polarity and mag nitude is applied to the averaging circuit 40. This error The chart motor 21.

signal is integrated by amplifier 47 and capacitor 44 since contact 1a is now closed during the time area a is scanned. Contact 1b is also closed thereby resetting the integrator consisting of amplifier 49 and capacitor 46.

After scanning area a the gauge 130 will begin scanning area b. Since only relay 2 is energized, a charge will accumulate on capacitor 45 through contacts 2a in an amount proportional to the deviation in sheet thickness above the target. Contacts 2b will likewise close and the integrated signal stored on capacitor 44 will be readout by means of line 54 to the control circuits at 60. Power will be applied to motor 76 through closed contacts 20 so as to cause a screw-down adjustment of the slice lip at the center of its right-hand segment controlling the stock thickness of area a. The time required for screw-down depends on the amount by which the stock sheet 100 has deviated above normal. Likewise as area is measured contacts 3c close to discharge capacitor 44, c'ontacts3b are closed to read-cu capacitor 45 for slice adjustment and contacts 3a close to permit the error signal tob'e integrated by amplifier 49 and capacitor 46. 7 Accordingly, adjustments of slice lip sections up or down are controlled automatically and immediately after each affected area is scanned. Stock density variations of the sheet 100 from the desired quantity are quickly and accurately corrected by this control system to maintain a relatively smooth profile of the desired thickness. The above described control system is only exemplary of an instance of paper control as this system may be used to regulate the profile of various other types of material. Also, from the foregoing, it will be apparent to those skilled inthe art, that various changes may be resorted to, without departing from the spirit or scope of the invention.

What is claimed is:

1. The combination, with a manufacturing machine for continuously producing alateraly extended length of a formed product, of flow regulating means for forming a cross-sectional dimension profile .of said product across the width thereof, said flow regulating means including a row of local profile adjustments each affecting said dimension at a portion of said width, said portion being substantially less than the total extent of said width, a plurality of actuators, each of said actuators being mechanically associated with a corresponding one of said local profile adjustments for driving the same in response to a control signal, means for gauging said dimension, means for mounting said gauging means on the product output side of said machine, traversing means associated with said mounting means for causing said gauging means to cyclically scan said product to and fro across said width thereof, means connected to said gauging means for generating a first signal indicative of said dimension at the traversing point of measurement, means for processing said signal to provide said control signal, and signal routing means controlled by said traversing means for routing said control signal to each of said actuators seriatim according to the lateral position of said gauging means with respect to said product.

.2. The combination of claim 1 wherein said signal processing means includes adjustable means for generating a second signal indicative of a desired value of said crosssectional. dimension, and means for integrating the difference between said first and second signals to obtain said control signal.

3. The combination, with a manufacturing machine for continuously processing a. lateraly extended length of a formed product, of a series of product condition determining means spaced across the width of said product, each of said means aifecting a condition of said product at a portion of said width, said portion being substantial- 137 less than the total extent of said width, adjusting means for each of said condition determining means, a plurality of actuators, each of said actuators being connected to a corresponding one of said adjusting means for driving the same in response to a control signal, means for gauging said condition, means for mounting said gauging means onthe product output side of said machine, traversing means associated with said mounting means for causing said gauging means to cyclically scan said product to and fro across said Width thereof, means connected to said gauging means for generating an error signal indicative of the deviation of said condition from a desired value thereof at the traversing point of measurement; first, second and third error signal averaging means each having integrat ing, readout, and reset modes of operation; signal routing means controlled by said traversing means for connecting said error signal to each of said averaging means sequentially in accordance with the lateral position of said gauging means with respect to said product, means controlled by said signal routing means for programming each of said averaging means sequentially through its integrating, readout and reset modes, means receiving the output of each of said averaging means only during said readout mode for generating said control signal in accordanee with the value of said output of said averaging means, and means associated with said signal routing means for connecting said control signal to each of said actuators in sequence.

4. The combination, with a manufacturing machine for continuously producing a laterally extended length of a formed product, of flow regulating means for forming a cross-sectional dimension profile of said product across the width thereof, said flow regulating means including a row of local'profile adjustments each affecting said dimension at a portion of saidwidth, said portion being substantially less than the total extent of said width, at sep arate reversible motor means for actuating each of said profile adjustments in response to a motor control signal, means for gauging said dimension, means for mounting said gauging means on the product output side of said ma-v chine, traversing means associated with said mounting means for causing said gauging means to cyclically scan said product to and fro across said width thereof, means connected to said gauging means for generating an error signal indicative of the deviation of said dimension from a desired value thereof at the traversing point of measurement; first, second and third error signal averaging means each having integrating, readout, and reset modes of operation; signal routing means controlled by said traversing means for connecting said error signal to each of said averaging means sequentially in accordance with the lateral position of said gauging means with respect to said product, means controlled by said signal routing means for programming each of said averaging means sequentially through its integrating, readout and reset modes, means receiving the output of each of said averaging means only during said readout mode for generating said motor control signal in accordance with the value of said output of said averaging means, and means associated with said signal routing means for connecting said motor control signal to said separate motor means in sequence.

References Cited in the file of this patent UNITED STATES PATENTS 

